1. Field
The subject matter disclosed herein relates to electronic devices, and more particularly to methods and apparatuses for use in and/or with a device capable of providing or otherwise supporting position, velocity, and/or time estimations.
2. Information
Wireless communication systems are fast becoming one of the most prevalent technologies in the digital information arena. Satellite and cellular telephone services and other like wireless communication networks may already span the entire globe. Additionally, new wireless systems (e.g., networks) of various types and sizes are added each day to provide connectivity among a plethora of devices, both fixed and portable. Many of these wireless systems are coupled together through other communication systems and resources to promote even more communication and sharing of information.
Another popular and increasingly important wireless technology includes navigation systems and in particular satellite positioning systems (SPS) such as, for example, the global positioning system (GPS) and other like Global Navigation Satellite Systems (GNSS). SPS enabled devices, for example, may receive wireless SPS signals that are transmitted by orbiting satellites of a GNSS and/or other ground based transmitting devices. The received SPS signals may, for example, be processed to determine a global time, a range or pseudorange, an approximate or accurate geographical location, altitude, and/or speed of the SPS enabled device. Consequently, various position and/or velocity estimation processes may be supported, at least in part, using an SPS enabled device.
SPS position tracking in certain environments, such as, “urban canyons” and the like, may become difficult as a result of SPS signals being reflected by objects and arriving over multiple paths at the receiver. Such multipath and other like signals may interfere with signals that travel along a line-of-sight (LOS) path from a transmitter, which may lead to position/velocity/time measurement errors. For example, such errors, when presented in a least-squares, Kalman filter (KF), and/or other like positioning process associated with a position/velocity/time estimation process, may lead to substantial position/velocity/time errors. By way of example, some pseudorange (PR) and/or pseudorange rate (PRR) measurement errors may lead to estimated position errors on the order of tens to hundreds of meters. It may be useful, therefore, to reduce or eliminate such errors at times.